Convert modem to serial port?

[John B. Milton]

In article <378 at balrog.UUCP> glg at balrog.UUCP (Gary L. Grebus) writes:
>Here's one for the hardware hackers...how hard would it be turn the 
>unix-pc 1200 baud modem into a serial port?  Is there a separate serial
>chip that could be hooked to the outside world, or is everything done by the
>modem chip?  Maybe the hard part of this would be kludging a the device
>driver to run it.

It should be relatively easy from the hardware point of view. The software
is another matter entirely. The serial port for the modem is the other half
of the NEC 7201 used for /dev/tty000. If you look at your major/minor numbers:

   0 crw-rw-rw-  2 uucp    mail      0,  0 Nov 28 21:34 /dev/tty000
   0 crw-rw-rw-  2 uucp    users     0,  2 Nov 27 20:00 /dev/tty001
   0 crw-rw-rw-  2 root    mail      0,  3 Nov  9 03:24 /dev/tty002
   0 crw-rw-rw-  2 root    users     0,  4 Jun 22 00:28 /dev/tty003
   0 crw-rw-rw-  2 root    users     0,  5 Jun 22 00:28 /dev/tty004
   0 crw-rw-rw-  2 root    users     0,  6 Jun 22 00:28 /dev/tty005
   0 crw-rw-rw-  2 root    users     0,  7 Jun 22 00:28 /dev/tty006

Your see that 0,1 is NOT used. Go ahead, make it. When you try to access it
you will get a kernel panic. (odd address I think)

The software is very nasty since the serial port is so buried in the phone
driver. I could imagine a way to eaves drop the serial line during normal
modem operation (for Tx Rx lights, for example), but not for generic serial
port usage.

John

-- 
John Bly Milton IV, jbm at uncle.UUCP, n8emr!uncle!jbm at osu-cis.cis.ohio-state.edu
(614) h:294-4823, w:459-7644;  MS-DOS is a beautiful flower that smells bad!